1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device. In particular, one embodiment of the present invention relates to a semiconductor device such as a sequential circuit that includes transistors having the same conductivity type and a semiconductor display device that includes the sequential circuit.
2. Description of the Related Art
A semiconductor display device in which a driver circuit is constituted of transistors having the same conductivity type is preferable because the manufacturing cost can be lowered. Patent Documents 1 and 2 disclose techniques for forming a variety of circuits such as inverters and shift registers that are used in driver circuits of semiconductor display devices and are constituted of transistors having the same conductivity type.